Critical Reasoning

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?
A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

bhumika.k.shah wrote:Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?
A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

IMO B

No, thephoenix,
that ain't the correct Answer. Kindly explain what made u choose B and eliminate the others.

thephoenix wrote:

bhumika.k.shah wrote:Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?
A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

IMO B

thephoenix wrote:
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.

IMO B

Infact I think this is not even relating to this passage.Plants in greenhouses grew more quickly than outdoor plants... so ???
there isnt any weakening attack in either of the school's plant growth

This is what i think. pardon me ! i may be wrong.

Sould be D. All the others are irrelevant or out of scope.

bhumika.k.shah wrote:Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Cause Effect

More sulphurdioxide slow plant growth

Stimulus indicates that even when cause did not occur, the effect occurred. That means there has to be an alternate cause for the stated effect. Lets find out the alternate cause for slow growth in urban school greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
Incorrect : Strengthens the argument. If urban school surroundings had less sulfur dioxide then plant growth would not be slow (as stated in the premise)

B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
Incorrect : Comparison between growth of plants in greenhouse and plants planted outdoors in plots is clearly out of scope.

C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
Incorrect : Issue is not about rural class or urban class. OUT OF SCOPE

D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
Correct : This shows an ALTERNATE CAUSE (grime on greenhouse windows, less light) for the stated effect.

E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.
Correct : How frequent the filters were changed is irrelevant to the scope of the argument.

Hope this helps : )

komal wrote:

bhumika.k.shah wrote:Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Cause Effect

More sulphurdioxide slow plant growth

Stimulus indicates that even when cause did not occur, the effect occurred. That means there has to be an alternate cause for the stated effect. Lets find out the alternate cause for slow growth in urban school greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
Correct : This shows an ALTERNATE CAUSE (grime on greenhouse windows, less light) for the stated effect.

Hope this helps : )

why we are trying to find out which one is weakening the argument .......
the q stem is asking for which one is helping to evaluate the result
how bth are same

[/quote]
why we are trying to find out which one is weakening the argument .......
the q stem is asking for which one is helping to evaluate the result
how bth are same[/quote]


And what is the result?

Result is that even when sulphur dioxide was filtered from the air, the urban school greenhouse plants still grew slowly. That means besides sulphur dioxide there must have been 'something ELSE' that led to slow growth in urban greenhouse plants. And (D) helps to evaluate the result by pointing at that 'something ELSE'

OA D

Hope komal's explanation did help you , thephoenix

I have been tossing around between B/D.

As for B, my thinking process is: Comparing with plants planted outdoors, plants within the greenhouse grow in a SO2 free environment. The fact that both of the plants grow much more quickly than those planted outside give a strong evidence that "SO2 causes a big difference in growth."

Imagine a different scenerio, they grow more or less at the same rate as plants planted outside, then eliminating SO2 has very little effect on the growth. We can think of other scenerios as well, say the difference between plants grown inside and outside of greenhouse in rural school is not as great as the difference in urban school, then it is an evidence that removing SO2 helps the growth in urban city more because of the higher content of SO2 in the air, to help to deduct that SO2 does affect the growth very noticeably...

As for D, it is unclear to me how it helps to evaluate the result:
Now that plants in urban area and rural area are both grown in a condition that the effect of SO2 has been eliminated, the result that those plants still grow at a different rate surely indicate a certain thing that some other factors, besides SO2, is affecting the growth rate. Option D merely gives one example for a long list of possible factors (temperature, pressure, amount of plants....) but that won't help to determine the effect of SO2.

To go even further, lights can have positive or negative effects on plants; some plants grow slowly when there is not sufficient light while there are some plants flourishing in a shadowed environment, that seems to give us another reason not to choose D.

I am having trouble with CR, not knowing if I should just let my mind flow in GMAT's logic way, forcing myself to accept the right answer, or I should stick to my own thinking and try to defend for myself, in which case I may enhance my GMAT-wrong thinking capability.

Please help.

Answer is D or E..what is the correct answer

It is D!

IMO, the answer is D
This is the only option that differentiates that there could be another factor responsible for slow growth of plants in urban area.

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

The two greenhouses were SIMILAR in one respect: each was filtered to eliminate sulfur dioxide.
Yet the plants in the urban greenhouse grew more slowly than those in the rural greenhouse.
Why?
To evaluate the result, we need to know whether there were any DIFFERENCES between the two greenhouses.

D. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.
This answer choice offers a key DIFFERENCE between the two greenhouses: since the urban greenhouse was covered with grime, the plants inside received less light than those contained in the rural greenhouse.

The correct answer is D.

Reasons to eliminate the other answer choices:

A: Irrelevant, since each greenhouse was filtered to ELIMINATE sulfur dioxide.

B: This answer choice offers a SIMILARITY between the two greenhouses.

C: The size of each class is irrelevant.

E: This answer choice merely confirms that the urban greenhouse more than likely eliminated sulfur dioxide from the internal air.

Can someone please explain why is not the answer E. Isn't it possible that the sulphar di oxide seeped into the greenhouse while changing filters more frequently ...